Decimal to binary converter Free
Convert whole decimal numbers of any size to binary, with optional 4- or 8-bit grouping and two’s complement at 8, 16, 32 or 64 bits.
Any length works. Spaces, underscores and a 0b prefix are ignored. Everything runs on your device.
About Decimal to binary converter
Type a whole number in base 10 and get its exact binary form. Very large numbers work too, because the conversion uses arbitrary-precision integers instead of floating point.
Negative numbers can be shown with a minus sign or as a two’s complement bit pattern at a fixed width, the way computers store signed integers. Grouping by 4 or 8 bits makes long results easier to read.
How to use it
- Enter a decimal number, such as 2026 or -42.
- Choose grouping and, for negative numbers, whether to use two’s complement and at which width.
- Copy the binary result, or press Swap to convert it back.
Good to know
- Numbers are converted with JavaScript BigInt, so there is no size limit beyond the 1,000,000-character input cap and your device’s memory.
- Two’s complement is offered at 8, 16, 32 and 64 bits. Values outside the chosen width are rejected rather than silently cut off.
- Text is always encoded as UTF-8. Other encodings such as UTF-16 or Latin-1 give different bytes for the same characters.
Questions and answers
How do I convert decimal to binary by hand?
Divide by 2 repeatedly and write down each remainder; reading the remainders from last to first gives the binary digits. For 10: 10÷2=5 r0, 5÷2=2 r1, 2÷2=1 r0, 1÷2=0 r1, so 10 is 1010.
What does two’s complement do with negative numbers?
It stores −n as 2^w − n at a width of w bits, so −1 in 8 bits is 11111111 and −128 is 10000000. The top bit acts as the sign.
Can I paste numbers with spaces, underscores or a prefix?
Yes. Spaces, tabs, line breaks and underscores are ignored, and a leading 0b (binary) or 0x (hex) prefix is accepted. If a character cannot be read, the error names it and its position.
Is my input sent anywhere?
No. Every conversion runs in your browser; nothing you type leaves your device.